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Abstract:

A signal receiving device includes: a first conversion unit comprising a
first input terminal to which a signal including a voltage signal and a
reference voltage is inputted, and a first output terminal which output a
first current signal voltage-current converted from the signal; a second
conversion unit comprising a second input terminal to which the reference
voltage is inputted, and a second output terminal which output a second
current signal voltage-current converted from the reference voltage; a
current mirror circuit comprising a third input terminal to which the
second current signal is inputted, and a third output terminal which
output a third current signal corresponding to the second current signal;
and an output unit connected to both the first and third output
terminals.

Claims:

1. A signal receiving device, comprising:a first conversion unit
comprising a first input terminal to which a signal including a voltage
signal and a reference voltage is inputted, and a first output terminal
which output a first current signal voltage-current converted from the
signal;a second conversion unit comprising a second input terminal to
which the reference voltage is inputted, and a second output terminal
which output a second current signal voltage-current converted from the
reference voltage;a current mirror circuit comprising a third input
terminal to which the second current signal is inputted, and a third
output terminal which output a third current signal corresponding to the
second current signal; andan output unit connected to both the first and
third output terminals.

2. The device according to claim 1, further comprising a voltage holding
unit connected to the first input terminal, the voltage holding unit
holding an applied voltage.

3. The device according to claim 1, further comprising a second voltage
holding unit connected to the second input terminal, the second voltage
holding unit holding an applied voltage.

4. The device according to claim 1, further comprising:a reference voltage
generation unit generating the reference voltage;a first switch
connecting the reference voltage generation unit and the first input
terminal; anda second switch connecting the reference voltage generation
unit and the second input terminal.

5. The device according to claim 4, further comprising:a third switch
connected between the reference voltage generation unit and the first
input terminal;a third voltage holding unit connected between the third
switch and the first switch;a fourth switch connected between the
reference voltage generation unit and the second switch;a fourth voltage
holding unit connected between the fourth switch and the second switch.

6. The device according to claim 5,wherein periods when the first and
third switches are ON do not overlap each other.

7. The device according to claim 5,wherein periods when the second and
fourth switches are ON do not overlap each other.

8. The device according to claim 4,wherein the reference voltage generated
by the reference voltage generation unit is variable.

9. The device according to claim 1,wherein the reference voltage is equal
to or lower than threshold voltages of the first and second conversion
units.

10. The device according to claim 1,wherein, when a voltage of the voltage
signal is larger than a predetermined voltage, a current outputted from
the output unit changes in correspondence with a change of the voltage of
the voltage signal.

11. The device according to claim 10,wherein the predetermined voltage
corresponds to a difference between the threshold voltages of the first
and second conversion units.

12. The device according to claim 1,wherein the voltage signal is one of a
pair of differential signals, andthe other of the pair of differential
signals and the reference voltage are inputted to the second input
terminal.

13. The device according to claim 1, further comprising:a fifth switch
making an input of the voltage signal to the first input terminal
continued or stopped;a detection unit detecting generation of an offset
voltage in the output unit, when the firth switch is making the input of
the voltage signal to the first input terminal stopped; andan adjustment
unit adjusting the offset voltage by controlling the current mirror
circuit or the second conversion unit, when the detection unit detects
generation of the offset voltage.

Description:

CROSS-REFERENCE TO THE RELATED APPLICATIONS

[0001]This application is based upon and claims the benefit of priority
from the prior Japanese Patent Application No. 2008-145054, filed on Jun.
2, 2008; the entire contents of which are incorporated herein by
reference.

[0005]A signal amplifier amplifying an inputted signal is in use (for
example, see JP-A2007-129501 (KOKAI)). In the signal amplifier described
in Document, a voltage signal inputted to a signal input terminal is
converted to a current by a transistor and outputted as a current signal
via a current mirror. On this occasion, if a voltage of the inputted
signal is lower than a threshold voltage of the transistor, the
transistor becomes in an OFF state, so that the outputted current is
zero. In other words, if an inputted signal is weak, it is difficult to
output a current from the signal amplifier.

BRIEF SUMMARY OF THE INVENTION

[0006]A signal receiving device according to an aspect of the present
invention includes: a first conversion unit comprising a first input
terminal to which a signal including a voltage signal and a reference
voltage is inputted, and a first output terminal which output a first
current signal voltage-current converted from the signal; a second
conversion unit comprising a second input terminal to which the reference
voltage is inputted, and a second output terminal which output a second
current signal voltage-current converted from the reference voltage; a
current mirror circuit comprising a third input terminal to which the
second current signal is inputted, and a third output terminal which
output a third current signal corresponding to the second current signal;
and an output unit connected to both the first and third output
terminals.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a block diagram showing a signal receiving device 100
according to a first embodiment.

[0008]FIG. 2 is a block diagram showing a signal receiving device 200
according to a second embodiment.

[0009]FIG. 3 is a block diagram showing a signal receiving device 300
according to a third embodiment.

[0010]FIG. 4 is a block diagram showing a signal receiving device 400
according to a fourth embodiment.

[0011]FIG. 5 is a block diagram showing a signal receiving device 500
according to a fifth embodiment.

[0012]FIG. 6 is a block diagram showing a signal receiving device 600
according to a sixth embodiment.

[0013]FIG. 7 is a block diagram showing a signal receiving device 700
according to a seventh embodiment.

[0014]FIG. 8 is a block diagram showing an application 1 of a signal
receiving apparatus.

[0015]FIG. 9 is a block diagram showing an application 2 of a signal
receiving apparatus.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016]Hereinafter, embodiments of the present invention will be described
in detail with reference to the drawings.

First Embodiment

[0017]FIG. 1 is a block diagram showing a signal receiving device 100
according to a first embodiment. The signal receiving device 100 includes
a signal receiving unit 110, a leak current compensation unit 120, a bias
voltage generation unit 130, and a signal output unit 141.

[0019]The leak current compensation unit 120 is constituted with a voltage
holding unit 121, a dummy voltage-current conversion unit 122, and a
current mirror unit 123. The voltage holding unit 121 is connected to the
dummy voltage-current conversion unit 122. The dummy voltage-current
conversion unit 122 is connected to the current mirror unit 123. The
voltage holding unit 121 and the dummy voltage-current conversion unit
122 are each grounded. The current mirror unit 123 is connected to the
voltage-current conversion unit 113, and a connection point thereof is
connected to the signal output unit 141.

[0020]The bias voltage generation unit 130 is constituted with a reference
voltage generation unit 131, switch units 132, 133, and a control signal
input unit 134. The reference voltage generation unit 131 is connected to
a connection point between the voltage-current conversion unit 113 and
the voltage holding unit 112 via the switch unit 132. The reference
voltage generation unit 131 is connected to a connection point between
the dummy voltage-current conversion unit 122 and the voltage holding
unit 121 via the switch unit 133. Control terminals of the switch units
132, 133 are connected to the control signal input unit 134.

[0023]The voltage-current conversion unit 113 and the dummy
voltage-current conversion unit 122 are elements, for example,
transistors, which convert inputted voltages into currents. It is
preferable that the voltage-current conversion unit 113 and the dummy
voltage-current conversion unit 122 are close in terms of threshold
voltages and leak currents. Therefore, it is preferable that transistors
of the same form are used for the voltage-current conversion unit 113 and
the dummy voltage-current conversion unit 122. Further, diversity of the
threshold voltage values due to manufacturing variance can be reduced by
dividing both the voltage-current conversion unit 113 and the dummy
voltage-current conversion unit 122 and disposing alternately and evenly.
The threshold voltages are limits of voltages which the voltage-current
conversion unit 113 and the dummy voltage-current conversion unit 122 can
convert to currents. The leak current is a comparatively weak current
outputted from the voltage-current conversion unit 113 (or the dummy
voltage-current conversion unit 122) at a time of a voltage equal to or
lower than the threshold voltage.

[0024]The current mirror unit 123 outputs to an output terminal a current
almost equal to a current which is inputted to an input terminal.

[0025]The control signal input unit 134 is an input terminal inputting a
control signal to control the switch units 132, 133. The switch units
132, 133 are turned ON/OFF in accordance with the control signal (ON
signal, OFF signal) and apply reference voltages to the voltage holding
units 112, 121. A pulse signal can be used as the control signal. It is
preferable that a duty ratio (period Ton of ON state/(period Ton of ON
state+period T off of OFF state)) of the pulse signal is small to some
degree. The smaller duty ratio of the pulse signal brings increased
periods of time for which the voltage holding units 112, 121 hold the
reference voltages. As a result, stability of an operation is maintained.

[0026]The reference voltage generation unit 131 generates a reference
voltage. It is preferable that the reference voltage is equal to or lower
than the threshold voltage of the voltage-current conversion unit 113, in
the interest of power consumption. It is also preferable that the
reference voltage is close to the threshold voltages of the
voltage-current conversion unit 113 and the dummy voltage-current
conversion unit 122. In this case, it can be considered to make the
respective transistors constituting the voltage-current conversion unit
113, the dummy voltage-current conversion unit 122 and the reference
voltage generation unit 131 have the same configuration. By using the
transistor having the same configuration as that of the voltage-current
conversion unit 113 for the reference voltage generation unit 131, it
becomes easy to make the reference voltage and the threshold value of the
voltage-current conversion unit 113 close to each other. Further,
creating the transistors of the same configuration simultaneously enables
compensation of manufacturing variance.

(Operation of Signal Receiving Device 100)

[0027]An operation of the signal receiving device 100 will be described.
The reference voltage generated in the reference voltage generation unit
131 is supplied to an input terminal of the voltage-current conversion
unit 113 via the switch unit 132. The same reference voltage is supplied
to an input terminal of the dummy voltage-current conversion unit 122 via
the switch unit 133. The voltages supplied to the respective input
terminals are held by the voltage holding units 112, 121. The switch
units 132, 133 are opened/closed intermittently by a control signal
inputted to the control signal input unit 134 and inject the reference
voltages to the voltage holding units 112, 121, to make the reference
voltages held. The reference voltage generated in the reference voltage
generation unit 131 is close to the threshold voltages of the
voltage-current conversion units 113, 122.

[0028]In a no signal input state (no signal is inputted to the signal
input unit 111), only the reference voltage (voltage close to the
threshold voltage) generated in the reference voltage generation unit 131
is applied to the input terminal of the voltage-current conversion unit
113. On this occasion, a leak current is outputted from the
voltage-current conversion unit 113.

[0029]On the other hand, the reference voltage generated in the reference
voltage generation unit 131 is also applied to the input terminal of the
dummy voltage-current conversion unit 122. On this occasion, a leak
current (almost the same as the leak current outputted from the
voltage-current conversion unit 113) is outputted from the dummy
voltage-current conversion unit 122.

[0030]The leak current outputted from the dummy voltage-current conversion
unit 122 is folded by the current mirror unit 123 and outputted from an
output terminal of the current mirror unit 123. A difference between an
output current of the current mirror unit 123 and an output current of
the voltage-current conversion unit 113 is outputted from the signal
output unit 141. As a result, no signal is outputted from the signal
output unit 141 at a time of no signal input.

[0031]When a signal is inputted to the signal input unit 111, the input
signal is inputted to the input terminal of the voltage-current
conversion unit 113 via the voltage holding unit 112. As stated above,
the reference voltage generated in the reference voltage generation unit
131 is applied to the input terminal of the voltage-current conversion
unit 113. Therefore, if the signal is inputted, a signal voltage is added
to the reference voltage. Therefore, a current made by adding the signal
and a leak current are outputted from the voltage-current conversion unit
113. On the other hand, the leak current outputted from the dummy
voltage-current conversion unit 122 is inputted to the input terminal of
the current mirror unit 123, folded, and outputted from its output
terminal. The difference between the output current of the current mirror
unit 123 and the output current of the voltage-current conversion unit
113 is outputted from the signal output unit 141. Therefore, only a
signal current component (made by removing a leak current component from
the current outputted from the voltage-current conversion unit 113) is
outputted from the output signal unit 141 at a signal input time.

[0032]As stated above, in the signal receiving device 100, even if an
input signal is a weak voltage signal, a current can be outputted
effectively and an error due to a leak current can be reduced.

Second Embodiment

[0033]FIG. 2 is a block diagram showing a signal receiving device 200
according to a second embodiment. The signal receiving device 200
includes a signal receiving unit 210, a leak voltage compensation unit
120, a bias voltage generation unit 130 and a signal output unit 141. The
signal receiving unit 210 has a signal detection unit 214 and a
current-voltage conversion unit 215 instead of the signal input unit 111
of the signal receiving device 100. An output terminal of the signal
detection unit 214, one end of which is grounded, is connected to a
voltage holding unit 112 via the current-voltage conversion unit 215. A
signal detection unit of a current output type can be used as the signal
detection unit 214. The current-voltage conversion unit 215 is grounded.
A capacitor, for example, can be used as the current-voltage conversion
unit 215.

[0034]A current signal generated in the signal detection unit 214 is
converted to a voltage in the current-voltage conversion unit 215, and
thereafter inputted to an input terminal of a voltage-current conversion
unit 113 via a voltage holding unit 112. In the signal receiving device
200, even if an input signal is a weak voltage signal, a current can be
outputted effectively and an error due to a leak current can be reduced.

Third Embodiment

[0035]FIG. 3 is a block diagram showing a signal receiving device 300
according to a third embodiment. The signal receiving device 300 includes
a signal receiving unit 110, a leak current compensation unit 120, a bias
voltage generation unit 330 and a signal output unit 141. In the bias
voltage generation unit 330, added to the bias voltage generation unit
130 in the first embodiment are switch units 335, 336, voltage holding
units 337, 338 and a control signal input unit 339. A reference voltage
generation unit 131 is connected to the voltage holding unit 337 via the
switch unit 335. The voltage holding unit 337 is connected to a
connection point between a voltage-current conversion unit 113 and a
voltage holding unit 112 in the signal receiving unit 110 via a switch
unit 132. The reference voltage generation unit 131 is connected to the
voltage holding unit 338 via the switch unit 336. The voltage holding
unit 338 is connected to a connection point between a dummy
voltage-current conversion unit 122 and a voltage holding unit 121 via a
switch unit 133. Control terminals of the switch units 132, 133 are
connected to a control signal input unit 134. Control terminals of the
switch units 335, 336 are connected to the control signal input unit 339.

(Operation of Signal Receiving Device 300)

[0036]Next, an operation of the bias voltage generation unit 330 in the
present embodiment will be described.

[0037]Control signals different from each other are inputted to the
control signal input units 134, 339. In other words, it is controlled so
that the switch units 132, 133 and the switch units 335, 336 are not in
ON states simultaneously by the control signals. It is preferable in a
viewpoint of stability that duty ratios of the control signals inputted
to the control signal input unit 134 and the control signal input unit
339 are small to some degree.

[0038]At a timing that an ON signal is inputted to the control signal
input unit 339, the switch units 335, 336 are turned ON. As a result, a
reference voltage generated in the reference voltage generation unit 131
is copied and held in the voltage holding units 337, 338 respectively. On
this occasion, since the signal inputted to the control signal input unit
134 is an OFF signal, the switch units 132, 133 become in OFF states.
Therefore, operations of the switch units 335, 336 do not influence the
signal receiving unit 110 or the leak current compensation unit 120. At a
timing that an ON signal is inputted to the control signal input unit
134, the switch units 132, 133 are turned ON. As a result, the voltages
having been held in the voltage holding units 337, 338 are copied and
held in the voltage holding units 112, 121 respectively. On this
occasion, since a signal inputted to the control signal input unit 339 is
an OFF signal, the switch units 335, 336 are in OFF states and do not
give influence, such as voltage escape to the reference voltage
generation unit 131. As a result, the voltage generated in the reference
voltage generation unit 131 can be stably given as a bias voltage to the
voltage-current conversion unit 113 and the dummy voltage-current
conversion unit 122.

[0039]When a voltage signal is inputted from a signal input unit 111, this
voltage signal is added to the reference voltage generated in the
reference voltage generation unit 131 and held in the voltage holding
unit 112. If a signal inputted to the control signal input unit 134 at
the above timing is an OFF signal, the voltage held in the voltage
holding unit 112 does not change. On the other hand, if the signal
inputted to the control signal input unit 134 is an ON signal, the switch
unit 132 becomes in an ON state. Therefore, part of the voltage signal
held in the voltage holding unit 112 is leaked to the voltage holding
unit 337. However, it is possible to reduce a leaking voltage signal by
making a retention volume (capacitance) of the voltage holding unit 337
small enough compared with a retention volume (capacitance) of the
voltage holding unit 112.

[0040]In the signal receiving device 300, even if an input signal is a
weak voltage signal, a leak voltage of the voltage signal to a bias
voltage generation unit can be made small. Therefore, it is possible to
hold an output signal effectively.

Fourth Embodiment

[0041]FIG. 4 is a circuit diagram showing a signal receiving device 400
according to a concrete example of a fourth embodiment. The signal
receiving device 400 has a configuration corresponding to the signal
receiving device 300 according to the third embodiment. A signal input
terminal 411, a capacitor 412 and a transistor 413 correspond to the
signal input unit 111, the voltage holding unit 112 and the
voltage-current conversion unit 113 respectively. A capacitor 421, a
transistor 422 and a current mirror circuit 423 correspond to the voltage
holding unit 121, the dummy voltage-current conversion unit 122 and the
current mirror unit 123 respectively. A reference voltage generation unit
431, transistors 432, 433, 435, 436, capacitors 437, 438 and pulse signal
input units 434, 439 correspond to the reference voltage generation unit
131, switch units 132, 133, 335, 336, the voltage holding units 337, 338
and the control signal input units 134, 339 respectively. The current
mirror circuit 423 is constituted with transistors 423a, 423b. The
reference voltage generation unit 431 is constituted with a constant
current source 431a and a transistor 431b.

[0042]The signal input terminal 411 is connected to a gate terminal of the
transistor 413 via the capacitor 412. A source terminal of the transistor
413 is grounded. A gate terminal of the transistor 422 is connected to
the grounded capacitor 421. A source terminal of the transistor 422 is
grounded. A drain terminal of the transistor 422 is connected to a drain
terminal of the transistor 423a of an input side of the current mirror
circuit 423. A gate terminal of the transistor 423a is connected to the
drain terminal of the transistor 423a and a gate terminal of the
transistor 423b, and a source terminal is connected to a power supply
terminal VDD. A drain terminal of the transistor 423b of an output side
of the current mirror circuit 423 is connected to a drain terminal of the
transistor 413, a connection point thereof being a signal output terminal
441. A source terminal of the transistor 423b is connected to the power
supply terminal VDD.

[0043]The constant current source 431a is connected to the power supply
terminal VDD and a drain terminal of the transistor 431b. The drain
terminal of the transistor 431b is connected to a gate terminal, and a
source terminal is grounded. Drain terminals of the transistor 435, 436
are connected to the drain terminal of the transistor 431b. Source
terminals of the transistors 435, 436 are connected to the capacitors
437, 438 respectively. The other terminals of the capacitor 437, 438 are
grounded. The source terminals of the transistors 435, 436 are connected
to drain terminals of the transistors 432, 433 respectively. Source
terminals of the transistors 432, 433 are connected to the gate terminals
of the transistors 413, 422 respectively. Gate terminals of the
transistors 435, 436 are connected to the pulse signal input unit 439,
while gate terminals of the transistors 432, 433 are connected to the
pulse signal input unit 434.

[0044]It is preferable that elements of the same form to each other are
used for the transistors 413, 422. This is for the sake that the
transistors 413, 422 become uniform in terms of threshold values and leak
currents. It is preferable that elements of the same form to each other
are used for the transistors 423a, 423b. This is in order to make
currents inputted /outputted to/from an input terminal and an output
terminal of the current mirror circuit 423 uniform.

[0045]It is preferable that an element with a smaller capacity value
(capacitance) compared with the capacitor 412 is used for the capacitor
437. This is in order to reduce a leak voltage from the capacitor 412 to
the capacitor 437.

[0046]It is preferable that an element with a smaller gate width or gate
number compared with the transistor 413 is used for the transistor 431b.
This is for the sake of lower power consumption of the transistor 431b,
and furthermore, of the entire signal receiving device 400.

(Operation of Signal Receiving Device 400)

[0047]Next, an operation of the signal receiving device 400 will be
described.

[0048]A predetermined current flows from the constant current source 431a
and supplied to the transistor 431b. The transistor 431b generates a
drain voltage corresponding to a supplied current value. The transistors
435, 436, 432, 433 function as switch circuits, becoming in ON states
when signals inputted to the pulse signal input units 439, 434 are ON
signals, and becoming in OFF states when the signals are OFF signals.

[0049]Different control signals are inputted to the respective pulse
signal input units 439, 434. The control signals are controlled so that
the transistors 435, 436 and the transistors 432, 433 do not become in ON
states simultaneously. It is preferable that duty ratios of the control
signals inputted to the pulse signal input units 439, 434 are small.

[0050]At a timing that an ON signal is inputted to the pulse signal input
unit 439, the transistors 435, 436 are turned ON. As a result, a drain
voltage generated in the transistor 431b is copied and held in the
respective capacitors 437, 438. On this occasion, since a signal inputted
to the pulse signal input unit 434 is an OFF signal, the transistors 432,
433 are in OFF states, not influencing the gate terminals of the
transistors 413, 422. At a timing that an ON signal is inputted to the
pulse signal input unit 434, the transistors 432, 433 are turned ON, the
voltages having been held in the capacitors 437, 438 are copied and held
in the capacitors 412, 421 respectively and applied to the gate terminals
of the transistors 413 and 422. On this occasion, since a signal inputted
to the pulse signal input unit 439 is an OFF signal, the transistors 435,
436 become in OFF states and voltage escape and the like to the
transistor 431b can be prevented. As a result, a reference voltage
generated in the transistor 431b is stably applied to the gate terminals
of the transistors 413 and 422 as a bias voltage.

[0051]In a no signal state, in which no signal is inputted to the signal
input terminal 411, equal bias voltages are applied to the gate terminals
of the transistors 413 and 422. Since the bias voltage has a value almost
equal to that of threshold voltages of the transistors 413 and 422, the
transistors 413 and 422 are in OFF states. On this occasion, a drain
current does not flow practically, but a subtle leak current occurs.

[0052]The leak current having occurred in the transistor 422 is inputted
to the input terminal of the current mirror circuit 423. A current of
almost the same value is outputted from the output terminal (drain
terminal of the transistor 423b) of the current mirror circuit 423 and
inputted to the drain terminal of the transistor 413.

[0053]The signal output terminal 441 outputs a difference between an
output current from the transistor 423b and an output current from the
transistor 413. Therefore, if the leak currents of the transistors 413
and 422 are equal, a signal corresponding to the leak current is not
outputted from the signal output terminal 441. In other words, at the
time of no signal input, no signal is outputted from the signal output
terminal 441.

[0054]When a voltage signal is inputted from the signal input terminal
411, a voltage of this voltage signal, being added to the reference
voltage generated in the transistor 431b, is applied to the gate of the
transistor 413. On this occasion, only a signal corresponding to the
inputted voltage signal is outputted from the signal output terminal 441.

[0055]As stated above, in the signal receiving device 400, even if an
input signal is a weak voltage signal, a current can be outputted
effectively. Further, an error due to a leak current can be reduced.

[0056]It should be noted that bias voltage values given to the transistors
413, 422 can be freely adjusted by adjusting a current value supplied in
the constant current source 413a. Thereby, input sensitivity can be
adjusted accordingly.

Fifth Embodiment

[0057]FIG. 5 is a block diagram showing a signal receiving device 500
according to a fifth embodiment. The signal receiving device 500 includes
a positive side receiving unit 510, a negative side receiving unit 520, a
bias voltage generation unit 530, a current mirror unit 541 and a signal
output unit 542. The positive side receiving unit 510 and the negative
side receiving unit 520 are differential signal receiving units. The
positive side receiving unit 510 is constituted with a signal detection
unit 511, a current-voltage conversion unit 512, a voltage holding unit
513 and a voltage-current conversion unit 514. The negative side
receiving unit 520 is constituted with a signal detection unit 521, a
current-voltage conversion unit 522, a voltage holding unit 523 and a
voltage-current conversion unit 524. The signal detection unit 511 is
connected to the voltage-current conversion unit 514 via the
current-voltage conversion unit 512 and the voltage holding unit 513. The
current-voltage conversion unit 512 and the voltage-current conversion
unit 514 are grounded. Meanwhile, the signal detection unit 521 is
connected to the voltage-current conversion unit 524 via the
current-voltage conversion unit 522 and the voltage holding unit 523. The
current-voltage conversion unit 522 and the voltage-current conversion
unit 524 are grounded.

(Operation of Signal Receiving Device 500)

[0058]An operation of the signal receiving device 500 will be described.

[0059]At a time of no signal input, in which no signal is inputted, no
change occurs to output terminals of the signal detection units 511, 521.
Therefore, no change occurs to the current-voltage conversion units 512,
522, either, and only bias voltages supplied from the bias voltage
generation unit 530 are applied to the voltage holding units 513, 523.
Therefore, the same current values are outputted from the voltage-current
conversion units 514, 524, and no signal output occurs in the signal
output unit 542 from which a difference between both the current values
is outputted.

[0061]Those voltage signals are added to the bias voltages held in the
voltage holding units 513, 523 respectively. Therefore, a voltage made by
adding a signal voltage to the bias voltage is applied to the
voltage-current conversion unit 514, so that an output current is
increased. Meanwhile, a voltage made by subtracting a signal voltage from
the bias voltage is applied to the voltage-current conversion unit 524,
so that an output current is decreased. A signal with twice a strength is
outputted from the signal output unit 542 from which the difference
between both the voltages is outputted.

[0062]Noises overlapping reception signals are outputted from the signal
detection units 511, 521 respectively as in-phase signals, and inputted
to the current-voltage conversion units 512, 522. Since a difference
between the in-phase signals is outputted from the signal output unit
542, a signal outputted therefrom does not include the noise.

[0063]In the signal receiving device 500, even if an input signal is a
weak signal, the signal can be detected as a differential signal, so that
a difference can be detected and outputted. Further, a noise is not
detected as a difference, so that the signal receiving device 500 is
resistant to noises.

Sixth Embodiment

[0064]FIG. 6 is a block diagram showing a signal receiving device 600
according to a sixth embodiment. There is shown an example in which an
antenna 651 and a differential output rectifier 642 are used as concrete
embodiments of the signal detection units 511, 522 in FIG. 5. When a
radio signal is inputted to the antenna 651, a current signal of a
differential is outputted by the differential output rectifier 652. When
the radio signal is received and the signal is detected by the
differential output rectifier 652, both efficiency and resistance to a
noise are secured.

Seventh Embodiment

[0065]FIG. 7 is a block diagram showing a signal receiving device 700
according to a seventh embodiment. The signal receiving device 700
includes an offset correction unit which performs correction when an
offset is generated in an output current of a voltage-current conversion
unit 113, an output current of a dummy voltage-current conversion unit
122, or the like. The offset correction unit is constituted with an
offset adjustment unit 761, switch units 762, 763 and an adjustment mode
switching signal input unit 764.

[0066]Output terminals of a signal output unit 141 and the dummy
voltage-current conversion unit 122 are each connected to the offset
adjustment unit 761 via the switch unit 762. The offset adjustment unit
761 is also connected to a current mirror unit 123 and the dummy
voltage-current conversion unit 122.

[0070]The switch unit 763 is connected between a signal input unit 111 and
a voltage holding unit 112, and further, is grounded. An input of a
voltage signal to an input terminal of the current-voltage conversion
unit 113 can be continued or stopped by the switch 763. The adjustment
mode switching signal input unit 764 is connected to the switches 762,
763.

(Operation of Signal Receiving Device 700)

[0071]Next, an operation of the offset compensation unit of the present
embodiment will be described. In a present configuration, as an operation
mode of the receiving device, a normal reception mode and an adjustment
mode can be switched.

[0072]In the reception mode, a similar operation to that in the signal
receiving device 100 is performed. On this occasion, an OFF signal is
inputted to the adjustment mode switching signal input unit 764, and the
switch unit 762 is in an OFF state while, as for the switch unit 763, the
signal input unit 111 and the voltage holding unit 112 are in a connected
sate.

[0073]In the adjustment mode, an ON signal is inputted to the adjustment
mode switching signal input unit 764. As a result, the switch unit 762
becomes in an ON state and the output terminals of the signal output unit
141 and the dummy voltage-current conversion unit 122 are each connected
to the offset adjustment unit 761. Meanwhile, the switch unit 763
separates the signal input unit 111 and the voltage holding unit 112 and
grounds the voltage holding unit 112. In the above state, the offset
adjustment unit 761 compares voltages generated in the signal output unit
141 and the output terminal of the dummy voltage-current conversion unit
122 in a no signal input state. When both the generated voltages are
different from each other (occurrence of an offset), the offset
adjustment unit 761 adjusts a current mirror unit 123 or a bias voltage
of the dummy voltage-current conversion unit 122, or the like so that the
offset is compensated. On this occasion, it is possible to set an offset
in the current mirror unit 123 or the bias voltage of the dummy
voltage-current conversion unit 122, or the like, in advance. Malfunction
by a certain degree of error can be prevented.

[0074]In the signal receiving device 700, an offset generated in the
signal output unit 141 can be adjusted. For example, an offset is
generated when characteristics of elements constituting the
voltage-current conversion unit 113, the dummy voltage-current conversion
unit 122 and the current mirror unit 123 are different due to
manufacturing variance, temperature change or the like.

[0075]As stated above, in the signal receiving device 700, it is possible
to detect a weak input signal effectively and at low power consumption
and perform a signal output, and to reduce an error due to a leak
current. As a result, it is possible to make a receiving device such as a
radio be of lower power consumption and of lower cost.

(Application 1)

[0076]Hereinafter, an application of a signal receiving device will be
described. FIG. 8 is a block diagram showing a system using a trigger
signal generator 10 including a signal receiving device 11. A signal
detection unit 21, the trigger signal generator 10, a power supply
control unit 24 and electronic equipment 23 are disposed. The trigger
signal generator 10 has the signal receiving device 11, a current-voltage
converter 12 and a battery 13.

[0077]The signal detection unit 21 is a voltage generation unit receiving
outside energy and generating electricity. The signal detection unit 21
is a rectifying circuit using a diode element or a MOS transistor, or a
photoelectric conversion element using a PN semiconductor element for
photovoltaic generation or the like. In other words, the signal detection
unit 21 includes at least an element capable of generating a direct
current voltage in correspondence with an input signal (for example, an
optical signal) from not-shown operating equipment.

[0078]When a photoelectric conversion element of a PN junction element of
a Si semiconductor is used as the signal detection unit 21, a P-type
semiconductor side is connected to a ground potential. An N-type
semiconductor side jointed to a P-type semiconductor is connected to the
trigger signal generator 10 as an output. When an optical signal is
inputted to the photoelectric conversion element, an electric potential
moves from a P-type semiconductor to an N-type semiconductor, so that an
electric potential of an output is made higher. In accordance with this
principle, an optical input signal is detected and a voltage in
correspondence with signal strength is generated as an output. When no
optical signal is inputted, a photoelectric effect does not occur and
movement of the electric charge is not generated. Since the electric
charge does not move and both the P-type and N-type semiconductors have
ground potentials, power consumption in the signal detection unit 21 is
not generated. Therefore, it is possible to wait for reception of an
optical signal without consuming electricity.

[0079]The signal receiving device 11 is a signal receiving device
constituted by eliminating the transistors 435, 436, capacitors 437, 438
and the pulse signal input unit 539 from the signal receiving device 400,
and corresponds to the signal receiving device 100 in terms of a
function. In other words, the signal receiving device 11 can also be
considered to be a concrete example of the signal receiving device 100.
It should be noted that the signal receiving devices 100 to 700 may be
also applied accordingly instead of the signal receiving device 11.

[0080]The trigger signal generator 10 acts by voltage generation of the
signal detection unit 21 in accordance with an input signal from the
not-shown operation equipment, and a trigger signal is outputted. As a
result, the power control unit 24 is controlled and the electronic
equipment 23 is activated. It should be noted that signal data can be
outputted from the signal detection unit 21 by using a signal column by
light emission/extinction of an optical signal.

(Application 2)

[0081]Next, another system using a trigger signal generator including a
signal receiving device will be described with reference to FIG. 9. In
FIG. 9, the same numerals and symbols are given to the same components as
the components in the drawings already described and description thereof
will be omitted. An internal configuration of a signal receiving device
11 is omitted to be shown. In this application, charging of a battery
power supply 13 is done by a trigger signal.

[0082]In FIG. 9, electronic equipment 23 and a power supply control unit
24 are supplied of electric power not from the battery power supply 13
but from an AC power supply 25. A charger 26 is also supplied of electric
power from the AC power supply 25. When a trigger signal is inputted from
an activation circuit 10 to the power supply control unit 24, a power
supply of the electronic equipment 23 is ON-controlled by the power
supply control unit 24. At the same time, a power supply of the charger
26 is ON-controlled by the power supply control unit 24. Thereby,
charging from the charger 26 to the battery power supply 13 is started.

[0083]In other words, when a power-on trigger signal is inputted from the
activation circuit 10 to the power supply control unit 24, the electronic
equipment 23 is activated by an output of the power supply control unit
24. The battery 26 is also activated by the output of the power supply
control unit 24, whereby an appropriate voltage is outputted from the
charger 26 and applied to a positive electrode of the battery power
supply 13. As a result, the battery power supply 13 is charged. The
electronic equipment 23, the power supply control unit 24 and the charger
26 are supplied of power supplies from, for example, the AC power supply
25 (or external DC power supply), whose output capacitance is larger than
that of the battery power supply 13.

[0084]When the output trigger signal of the activation circuit 10 is in an
OFF state, the power supply control unit 24 is in an OFF state.
Therefore, the electronic equipment 23 and the charger 26 are also in OFF
states, so that electric power of the AC power supply is not consumed.

[0085]In this application 2, the battery power supply 13 is charged from
the charger 26 when the electronic equipment 23 is in a power-on state.
As a result, the battery power supply 13 is charged automatically when
the electronic equipment 23 is in the power-on state, so that an exchange
due to battery exhaustion of the battery power supply 13 becomes almost
unnecessary.

(Other Applications)

[0086]Additional advantages and modifications will readily occur to those
skilled in the art. Therefore, the invention in its broader aspects is
not limited to the specific details and representative embodiments shown
and described herein. Accordingly, various modifications may be made
without departing from the spirit or scope of the general inventive
concept as defined by the appended claims and their equivalents.

Patent applications by Shoji Otaka, Yokohama-Shi JP

Patent applications by Toshiyuki Umeda, Inagi-Shi JP

Patent applications by KABUSHIKI KAISHA TOSHIBA

Patent applications in class Converting input voltage to output current or vice versa

Patent applications in all subclasses Converting input voltage to output current or vice versa